In which of the following situations, does the list of numbers involved make an arithmetic progression, and why ? :- The taxi fare after each km when the fare is $ 15 for the first km and $ 8 for each additional km.

In which of the following situations, does the list of numbers involved make an arithmetic progression, and why ? :-The cost of digging a well after every metre of digging, when it costs $150 for the first metre and rises by $50 for each subsequent metre.

In which of the following situations, does the list of numbers involved make an arithmetic progression, and why ? :- The amount of air present in a cylinder when a vacuum pump removes 1/4 of the air remaining in the cylinder at a time.

In which of the following situations, does the list of numbers involved make an arithmetic progression, and why ? :- The amount of money in the account every year when ? 10000 is deposited at compound interest at 8% per annum.

Form the pair of linear equations in the following problems and find their solutions (if they exist) by any algebraic method :-Places A and B are 80 km apart from each other on a highway. A car starts from A and another from B at the same time. If they move in the same direction they meet in 8 hours , and if they move in opposite direction, they meet in 1 hour and 20 minutes respectively. Find the speed of the cars.

Two trains leave a railway station at the same time. The first train travels due west and the second due north. The first train travels 5 km/hr faster than the second train. If after two hours, they are 50 km apart, find the average speed of each train.